1. FIELD OF THE INVENTION
The present invention relates to a cleaning system for a mud separator, used in conjunction with, for example, the drilling or workover of a subterranean well.
2. DESCRIPTION OF THE PRIOR ART
During the drilling of a subterranean well, drilling fluid, or mud, is circulated into and throughout the well. The mud serves to cool the bit and to carry cuttings away from the bottom of the bore hole. Typically, a drilling mud comprises a viscous suspension of barite. As the mud circulates, it becomes contaminated with gases, cuttings, and other particulates. It is therefore necessary to treat the mud chemically and mechanically before recirculating it to the bore hole.
For such mechanical treatment, common filters or centrifuges have, by themselves, proved inadequate. The high viscosity tendency to gel which are desirable qualities in a drilling fluid or mud militate against normal centrifugal separation.
A separator as disclosed in U.S. Pat. No. 3,400,819 to Burdyn has proved effective for mechanical treatment of such mud. In general, such a mud separator comprises a substantially cylindrical, perforated mud barrel which is rotated within a pressure tight chamber. A fluid pressure differential is created in the separator in a direction to oppose the centrifugal action caused by the rotating mud barrel. Mud is introduced within the pressure tight chamber. A portion of the mud is accelerated by the rotating mud barrel, and is thus subject to both centrifugal action and a pressure differential tending to effect flow in an opposite direction. By varying the speed of rotation, rate of mud flow, and other factors, the degree of particle separation may be controlled. The mud separator is fed by a mud pump. The pump has inlet valves to control the flow of water and mud into the pump. Depending on their position, the mud pump will circulate mud to the separator for processing, or water for dilution or flushing. When a mud separator is shut down for whatever reason, the barite will settle out of the mud suspension, unless the separator is properly flushed with water. This deposit of barite will create an inbalance in the mud barrel. Subsequent operation of the unbalanced mud barrel will greatly reduce the life of its bearings and associated rotary sealing units.
Heretofore, a major concern with such mud separators has been maintenance cost due to the short life of seals, bearings and associated components. When the separator is manually shut down, manual cleaning may be neglected. In case of an overload on the motor, a current sensing relay trips the motor off circuit. In either case, settling of barite and consequent inbalance in the rotating mud barrel have occured. Accordingly, there is a need for an automatic cleaning system which will close the mud valve and open the water valve to the mud pump, thus effecting a flushing cycle, each time the mud separator is shut off, or when the mud barrel begins to plug up, thus overloading the drive motor.